Articulation Loss of CONSonants (%-Alcons) One method of objectively measuring speech intelligibility is Articulation Loss of CONSonants (%-Alcons), showing the number of consonants being missed as a percentage. Consonants play a much more significant role in speech intelligibility than vowels. If the consonants are heard clearly, the speech can be understood more easily.

Dn,c,w (dB) Single value, according to EN ISO 717-1, for the laboratory sound insulation of a suspended ceiling between two rooms, measured according to ISO 140-9. This measurement takes only into account the sound transmission through the suspended ceiling.

Flutter echo Occurs when noise bounces between parallel surfaces in a room.

Rapid Speech Transmission Index (RASTI) RASTI is an objective way of measuring speech intelligibility. It is measured at two frequencies, 500 and 2000 Hz, by placing a loudspeaker, which transmits sound from the location of the person speaking, and a microphone where the listeners are situated. (See also STI).

Sabine The physicist Wallace Clement Sabine (1869-1919) created in Riverbank, west of Chicago, the well known Sabine formula (T=0,16V/A), showing the relationship between reverberation time (T s), room volume (V m³) and the amount of absorption (A m²).(image): (Sabine's formula)

Speech Transmission Index (STI) Similar to the RASTI method but a more complete form of measuring speech intelligibility by measuring all octave bands in the frequency range 125-8000 Hz.